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Date: Wed, 25 Apr 2007 09:24:56 -0400
From: "Craig Falls" <cfalls@gmail.com>
To: caml-list@yquem.inria.fr
Subject: possible infinite loop in compiler
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X-Spam: no; 0.00; compiler:01 stack:01 ocamlc:01 ocamlopt:01 foo:01 sig:01 foo:01 struct:01 sig:01 struct:01 mismatch:01 constraint:01 constraint:01 modules:02 match:02 

The following code blows the stack in ocamlc and ocamlopt 3.09.3:

module Foo : sig
   type 'a t = private 'a constraint 'a = [< `foo ]
 end = struct
   type 'a t = 'a constraint 'a = [< `foo ]
 end

Other row types such as [> `foo ] also cause the error.  The following
version returns a confusing (to me) error message:

module Foo : sig
   type 'a t = private 'a constraint 'a = [< `foo ]
 end = struct
   type 'a t = private 'a constraint 'a = [< `foo ]
 end

Signature mismatch:
 Modules do not match:
   sig type 'a t = private 'a constraint 'a = [< `foo ] end
 is not included in
   sig type 'a t = private 'a constraint 'a = [< `foo ] end
 Type declarations do not match:
   type 'a t = private 'a constraint 'a = [< `foo ]
 is not included in
   type 'a t constraint 'a = [< `foo ]